http://nopr.niscair.res.in/handle/123456789/801 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/2185 Title: Determination of pKa’s of hydroxamic acids by nucleophilic substitution reaction <br/> <br/>Authors: Shrivastava, Ashish; Ghosh, Kallol K <br/> <br/>Abstract: Acid dissociation constant (pKa) of some para-substituted benzohydroxamic, 4-XC₆H₄CONHOH, and N-methyl para-substituted benzohydroxamic acids, 4- XC₆H₄CON(OH)CH₃, where X = H, CH₃, CH₃O, NO₂, Cl, have been determined spectrophotometrically by nucleophilic substitution reactions of p-nitrophenyl acetate with hydroxamate ions at 27± 0.1ºC. All reactions in this study follow pseudo-first order kinetics under condition of excess nucleophile. Good correlation has been observed between pKa and substitutent constants pointing out the validity of the Hammett equation. The kinetics results have been discussed on the basis of pKa and ⍺-effect of hydroxamic acids. <br/> <br/>Page(s): 1630-1634 http://nopr.niscair.res.in/handle/123456789/2184 Title: Spectrophotometric determination of nickel(II) with 2-hydroxy-3-methoxy-benzaldehyde thiosemicarbazone <br/> <br/>Authors: Kumar, A Praveen; Reddy, P Raveendra; Reddy, V Krishna <br/> <br/>Abstract: 2-Hydroxy-3-methoxy benzaldehyde thiosemicarbazone has been synthesized, characterized and its analytical application investigated. It reacts with nickel(II) in aqueous solution at pH 4.0-8.0 and at room temperature to form a yellow coloured ML (1:1) complex with absorption maximum at 410 nm and molar absorptivity 2.0510⁴ l mol⁻¹ cm⁻¹. Beer’s law is obeyed in the range of 0.058-2.347 μg ml⁻¹ of Ni(II). A method for the determination of nickel(II) by second order derivative spectrophotometry has also been proposed. Interference of various diverse ions has been studied. The proposed methods have been successfully applied to determination of nickel in aluminium-based steels, drinking water, plant samples and in vegetable oil. <br/> <br/>Page(s): 1625-1629 http://nopr.niscair.res.in/handle/123456789/2183 Title: Spectrophotometric determination of hydrazine using bromine and methyl red <br/> <br/>Authors: George, Mary; Nagaraja, K S,; Balasubramanian, N <br/> <br/>Abstract: Hydrazine has been determined by its oxidation to nitrogen with a known excess of bromine. Bromine in acidic medium bleaches the dye methyl red. A known excess of bromine when treated with hydrazine is reduced to bromide and the unreacted bromine is determined using methyl red. The molar absorptivity is calculated to be 9.95 x10⁴ L mol⁻¹cm⁻¹. The method obeys Beer’s law in the range 0-6 μg of hydrazine in an overall aqueous volume of 25 mL with a correlation coefficient of 0.999.The detection limit is 0.25μg of sample. The relative standard deviation is 2.7% (n=10) at 3 μg of hydrazine. Interferences due to various foreign ions have been studied. The proposed method has been successfully applied for the estimation of hydrazine in boiler feed water samples. The results obtained in the developed method compare well with the p-dimethylaminobenzaldehyde (p-DAB) method and by the recovery studies of added hydrazine. <br/> <br/>Page(s): 1621-1624 http://nopr.niscair.res.in/handle/123456789/2182 Title: Rapid analysis of americium and plutonium in environmental samples by alpha-spectrometry <br/> <br/>Authors: Amoli, H Salar; Barker, J <br/> <br/>Abstract: A new method to assay americium and plutonium in soil samples is reported here. Using the method, it is possible to have a uniform and thin layer of the sample on alpha-spectrometer disc by electroplating. Prior to electrodeposition, the sample is separated by short column chromatography. A current of 900 mA and a plating time of 90 min in the pH range 2–2.5 have been found to be the best conditions for the deposition of americium. Optimum conditions for separation and electrodeposition of plutonium from soil samples have also been obtained. The modified procedures have been successfully applied for the simultaneous determination of Am and Pu. <br/> <br/>Page(s): 1618-1620